The US Open may cease to be free and open to tennis fans who watch it solely on the web.

Online viewership of the tournament has grown so large that organizers are considering charging for computer and mobile viewing. USOpen.org is one of the few major sports destinations that offers fans completely free coverage of live games on iPhones, iPads and now Android-powered phones.

The US Tennis Association, which holds the annual tourna ment in Flushing Meadows Park, is mulling the move as its TV partners — ESPN2, CBS and the Tennis Channel — move ahead in developing their own digital delivery of matches.

“We offer more free ways than any other sporting event. We’re a not-for- profit with a mis sion to promote and develop ten nis,” Smith said. “Would we like to monetize it in the future? Of course, we will, but we’ll al- ways take a balanced approach.”

At this point, officials haven’t decided whether to charge consumers or seek additional fees from their TV-network partners, who would pass the cost on to consumers.

Right now, USOpen.org offers live streams of every televised match in the tournament, giving viewers little reason to go elsewhere on the Web.

While ESPN offers matches at ESPN3.com, digital delivery is available only to viewers who are willing to verify that they are a paying cable or satellite-TV subscriber.

CBS will show matches at CBSSports.com but only when it coincides with its weekend TV coverage of the tournament starting this Saturday. The Tennis Channel doesn’t offer live matches online.

Web traffic during last year’s Grand Slam hit 12.4 million unique visitors, while there were 40 million total visits to the USopen.org. Viewers streamed 2.8 million hours of footage online during last year’s tournament.

Meanwhile, attendance at the US Open last year topped 700,000, with 97 percent of tickets sold.

“It’s about reaching a broader audience,” said one major sports consultant.

The nonprofit organization is also reaping ad dollars, pulling in an estimated $75 million from sponsors, up from $60 million two years ago.

The US Open kicked off yesterday with Alec Baldwin, hurdler Edwin Moses and model Bridget Moynahan slated to attend its opening festivities. A host of Wall Street bigwigs will also be present, including JPMorgan boss Jamie Dimon.